Upload a binary file with vb.net from an xml node

I'm trying to upload binary file into an oracle blob field. I retrieve the binary file from an XML document loaded in memory. I'll try to explain this in detail:

1) A page builds an XMLDocument with client code. In a node of this document, it sets the type to binary and attach a local filesystem document. Then, assigns the value to an hidden input field and sends it to itself 2) This page receives the post data, selects the binary content of the xml node and try to insert the binary data into the blob field (server side code).